Paul Carus 
Foundations of Mathematics [PDF ebook] 
A Contribution to the Philosophy of Geometry

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. I need not mention here perhaps, Since it is a fact of no consequence, that the readings of the several manuscripts vary, and that some proposi tions (e. G., that all right angles are equal to one another) are now missing, now counted among the postulates, and now adduced as common notions. The commentators of Euclid who did not under stand the difference between Postulates and Com mon Notions, spoke of both as axioms, and even to-day the term Common Notion is mostly so trans lated.